As you mentioned in the other thread, your The Sims 3 mouse option is still on.
Could you try taking your 'Options.ini' out of Documents\Electronic Arts\The Sims 4?
Start the game, you'll notice your options all have been reset, try seeing if turning the Sims 3 mouse on fixes the problem.
If not, you can choose to put the file back and overwrite the new one the game made.
Thanks for the suggestion Phantomlover1717 but its has not worked unfortunately ☹️
I would suggest just trying a different mouse. Maybe this one has something wrong when you click on the middle mouse button. Or maybe even restarting your computer or taking out the usb of the mouse and plugging it back in will help.
